Time division multiplex telephone system



Jan. 20, 1948. c. H. HOMRIGHOUS- 3 ,6 7

TIME DIVISION MULTIPLEX TELEPHONE SYSTEM Filed Sept. 28, 1943 2 Sheets-Sheet 1 Jan. 20, 1948. c. H. HOMRIGHOUS TIME DIVISION MULTIPLEX TELEPHONE SYSTEM Filed Sept. 28, 1943 2 Sheets-Sheet 2 vide in a party telephone line Patented Jan. 20, 1948 TIME DIVISION MULTIPLEX TELEPHONE SYSTEM Charles H. Homrighous, Oak Park, 111. Application September 28,1943, Serial No. 504,121

9 Claims. (Cl. 17915) This invention relates to transmitting two two-way telephone messages over a line at the same time.

One of the main objects of my invention is to double the number of messages that may be transmitted over trunk lines between telephone ofiices.

Another object of my invention is to provide a system for intermittently transmitting two telephone messages over a subscribers telephone line.

Another object of my invention is to provide a two message two-way trunkhaving means for allotting each message different recurring periods of time.

Another object of my inventionis to provide a two message two-way trunk with means for signalling in either direction.

Another object of my invention is to provide in a party telephone line means for transmitting at least two private two-way telephone messages simultaneously.

Still another object of my invention is to promeans for notifying the operator which party is calling.

Several telephone messages may be transmitted simultaneously over a pair of conductors by providing a different carrier wave for each telephone message. In the instant invention I separate the sound signals for two messages into equal portions or fragments and by reducing the period of time for each fragment approximately one half, the two messages may be transmitted in rotation over a pair of conductors.

The various objects and features of my invention will be clear from the following description taken in accordance with the accompanying drawing in which:

Figure 1 is a simplified diagram of a private two party subscribers line.

Figure 2 is a simplified diagram of a twomessage two-way trunk line.

Figure 3 shows the interval reducing and expanding mechanism with associated circuits that may be used at the subscribers station.

Figure 4 shows the interval reducing and expanding mechanism with associated circuits that may be used at the switchboard.

Figure 5 shows accord circuit that may be used with this invention.

Figures 6 and 7 are detail views.

Figure 1 represents a two party subscribers telephone line having means at the switchboard terminal whereby an operator may individually signal each station on the line, also means whereby either station may signal the operator at the switchboard, indicating which subscriber is calling. The numeral I represents subscribers station mechanism and associated circuits for separating the outgoing sound signals into equal portions or fragments and then reducing the pe-'- a telephone system for V riod of time of each portion of signals to approximately one half to transmit the signals for one message in alternate periods of time. The mechanism also combines the incoming sound signals by expanding or doubling the interval of time for each portion of incoming signals. The numeral I' represents similar equipment for a second party on the same line, to be fully explained later.

The mechanism 2 and 2 and their associated circuits at the telephone oflice are similar to the subscriber's station equipment and may function to separate and combine two different telephone messages.

Figure 2 shows a two conductor trunk line extending between two telephone oflices and terminating in two jacks at each oifice for two secret telephone conversations at the same time.

Figure 3 shows the mechanism and associated circuits represented by the numerals I and I in Figures 1 and 2. Speech currents representing a conversation are produced as a result of speaking into the microphone 3. The speech current or sound signals from the microphone 3 are applied through the transformer winding 4, junction contact 5, recording coil 6, transformer windmg I, junction contact 8 and battery 9. The recording coil 6 will impress magnetic variations in the endless telegraphone wire I0 traveling at a uniform speed beneath the 'coil in accordance with the speech currents produced by the microphone 3. Beneath the wire ID are two reproducing coils II and I2 traveling on a belt in an opposite direction to the moving wire and at approximately the same speed that the wire is moving. The message variations are reproduced in the coil II traveling between lines or points I3 and I4. Therefore the sound signal frequency will be approximately doubled or the period of time for the portion or fragment of the message will be reduced by one half. The coils II and I2 are spaced'so that message variations will be reproduced in alternate periods of time; that is,

. after coil I I reproduces one portion of the message an equal period of time will elapse before coil I2 starts to reproduce the message variations from the wire I0. 7 I

The current variations produced in coils I I and I2 are applied through brushes not shown contacting the bars I5 and I8, conductors IT, to the electromagnet I8, thereby actuating the microphone I9 to redevelop speech current in the line circuit to the telephone oifice, through winding 2| of anti-side tone transformer, line conductor 22, telephone ofiioe equipment of Figure 4, line con ductor 23, relay 43, resistor 49, and switch hook contacts 24. Thus the speech currentsproduced by the microphone 3 will be reproduced and transmitted over the line circuit in alternate periods oftime. Y

Speech current incoming from the line conductors 22 and 23 during alternate periods of time pass through transformer windings El, 25 and 26 in series and condenser 21'. The variable currents in winding 25 are applied to the recording coils 28 and 29, over conductors 39, bars 3! and 32. The coils 28 and 29 travel on a belt beneath the telegraphone wire 33 in a direction opposite to the movement of the wire. This mechanism is similar to the mechanism described above, both mechanisms being connected together and driven by a single motor, except that the problem now is to expand the intervals for portions of the incoming messages. The rotating coils 28 and 29 will impress magnetic variations in the wire 33 between the points or lines I3 and I4 during alternate periods of time. Therefore, since the coils 28 and 29 and the wire 33 are moving in opposite directions the message variations reproduced in coil 34 are expanded to approximately equal their original intervals.

The current variations in coil 35 are applied to the transformer winding 35, producing a variable current in the telephone receiver 36. Coils 31 and 38 are erasing coils.

The signal separating and combining devices comprising the telegraphone wires IE! and 33 which may be the same Wire and the coils i I, I2, 28 and 29 are driven by a single motor at the subscribers station. The motor, not shown,

. drives the cam wheel 39 through a friction clutch indicated by the dotted circle 49. .The cam wheel 39 through an intermediate gear drives the pulley '4I which is directly connected to the pulley G2. Thus both the sending mechanism and receiving :mechanism are driven at the same speed. The speedier the wheels 39 and l! is approximately ten R. P. S. v a

The line circuit is supplied with twenty-four and forty-eight volts from the telephone otlice batteries, (Figure 4) in successive rotation and during equal periods of time to be fully explained later. The armature of relay 43 will be operated only during the time that forty-eight volts are connected to the line. The energization of relay 43 places ground potential on the control relay M through cam controlledcontacts 35. The operation of the armature of relay 44 draws the holding bar 46 out of engagement with the pin 41, thus allowing the wheels 39, ii and 52 to rotate, whereby a portion or fragment of a conversation may be sent over the line circuit during one half revolution of the wheel 39. Whereupon the cam controlled contacts 48 are opened for the remaining one half revolution of the wheel 39. Opening the contacts 48 placesthe resistance 49 in series'with the anti-side tone transformer during the 24 volt period. It is also to be noted that the coils II and 28 have traveied from line I3 to line I l during one half revolution of wheels ll and 42 and-during the remaining half revolution of the wheels none of the rotating coilsare engaging or coacting with the continuously moving wires I and I3.

The generator 59. (Figure 4) develops ten cycles per second sine wavecurrent whichis applied to the device for producing square waves.

. The positive pulse of the square wave is applied 5 tothe relay 52 for energizing the relay during one half of each cycle, therebyinterchanging i from twenty-four to forty-eight volt transmission during each'cycle 'of generated'current, or forty-- fei'ght volts .duringone half revclutionof the wheel 39 and twenty-four volts during 3 the other one half revolution of the Wheel.

The subscribers station equipment for the second party I on the line extending to the control office is exactly like that described above except for the wheel 39 which would be replaced by a wheel 53 Figure 6 having the location of the holding pin 41 on the opposite side of the wheel and the cam for opening the contacts 18' on the opposite side of the wheel so that the contacts 48 for the station I will be open to include resistance 54 in series with the transformer at station I during the time that the contacts 48 in station are closed. The coil 28 would be as shown in Figure 6 at start of forty-eight volt transmission. Therefore, station I will transmit on forty-eight volts and station I will transmit on twenty-four volts. The relay 55, like relay 43, operates only on forty-eight volts and controls a relay similar to M in station I.

The ringer 55 in station I may be for thirtythree cycle current and the ringer 51 in station I may only respond to sixty-six cycle current.

Figure 4 shows the mechanism and associated circuits represented by the numerals 2 and 2 in Figures 1 and 2. The mechanism and associated circuits in Figure 4 are similar to those in Figure 3 and the operation is practically the same.

The speech currents from the operators or called subscriber's microphone are applied through the cord circuit (Figure 5), jack 58 to the recording coil 59. The recording coil 59 will impress magnetic variations in the endless telegraphone wire 60 traveling at a uniform speed beneath the coil. Beneath the wire 59 are two reproducing coils BI and 62 traveling on a belt in the opposite direction to the moving wire and at approximately the same speed as the speed of the wire. The message variations reproduced in the coils 5| and 62 will have their frequency practically doubled or the period of time for each fragment of a message will be reduced by one half. The coils BI and 62 are spaced so that message variations will be produced in alternate periods of time as described above for the subscribers station. The current variation produced in coils 6| and 92 are applied through brushes contacting bars 63 and 6A, conductors (55, to the electromagnet 66 for actuating the microphone 61 to develop speech current in the line circuit to the subscribers station through windings 68 of the anti-side tone transformer, contact 10, contact II when relay 52 is energized, line conductors 22 and 23, to forty-eight volt battery. Thus the speech produced at the operators microphone or at a called subscribers station will be reproduced and transmitted over the line circuit during alternate periods of time.

Speech currents incoming from the calling subscribers station during alternate periods of time flow through the transformer windings 68, I2 and I3, condenser 14. The variable current in wind ing I2 is applied to the recording coils l5 and i6 alternately through conductors I1 and bars I8 and 19. The coils l5 and 16 travel on a belt beneath the continuously moving wire 89 in a direction opposite to the movement of the wire. This mechanism is similar to the mechanism associated with coils GI and 62, both mechanism being connected together and driven by a single motor at the telephone ofiice.

The rotating coils I5 and 16 will impress magnetic variations in the wire 85 during alternate periods of time. The wire and coils I5 and .16 travel in opposite directions, therefore the message variations reproduced in coil 8| are expanded to approximately equal their original interval.

The current variations in coil 8I are applied to the transformer winding 82 producing a var- Figure 7 shows the arrangement of the wheels 85' and 01' for the equipment 2'. The coil I5 would be in the location shown at the start of the 48 volt transmission period.

From the above description it has been shown that a conversation between two stations may be transmitted over the two conductor line during alternate periods of time.

The telephone office equipment for the second station 2 in Figures 1 and 2 is exactly like the office equipment described in Figure 4 except that twenty-four volt current is supplied to the line over conductors 89 and 90 during the intermediate periods of time, whereby a second conversation may be transmitted during the periods intervening the first message.

To synchronize the subscriber's station mechanism with the mechanism at the telephone office: The relay 52, which upon energizing, places 48 volts on the line, actuating the relay 43 to in turn actuate the control relay 44 and a similar control relay 55 in station I is actuated in unison with relay 43 as previously described. Relay 52 upon energizin also places ground through its contacts 9| over conductor 92 and cam controlled springs 93, to the control relay 94, thereby releasing the rotating mechanism at the telephone oifice at the same instant that the mechanism at the subscribers station is released. The conductor 95 places ground potential on the control magnet 96 in the office equipment 2' Figure 7.

The wheel 39 Figure 3 is driven at a slightly greater speed than ten R. P, S. so that the holding bar 46 will have a tendency to snub or slow down the speed of the wheel at the end of each revolution. Assuming that a calling subscriber removes the receiver from the switch hook some time after the start of 48 volt transmission the relay 44 would be operated as previously described, which would release the wheel 39 after the start of transmission.

The springs of relay 43 are controlled by a ratchet 91 pivoted on the end of the armature 98. As the armature is attracted to the pole of the coil the springs are closed by the ratchet engaging the bottom of spring 99; further movement of the armature causes the ratchet arm to engage a pin I00, thereby releasing the spring 99, but still maintaining its armature in an operated position. Therefore, the relay 43 upon energizing after the wheel 39 has rotated less than a complete revolution will have no effect on the control relay 44, since contacts 45 are open and the springs of relay 43 are only closed when the relay is first energized. The wheel 39 will then come to rest with the holding bar 46 engaging the pin 41 until the start of the next period of 48 volt transmission and from this time on the wheel 39 will rotate in synchronism with the wheel 05. V The mechanism for station I' is similarly H synchronized.

Figure 5 shows a conventional cord circuit provided with a signal lamp I M to indicate when the calling party hangs up his receiver, and a ringing key I02 for signalling a called subscriber. The operator, upon inserting the plug I03 in the jack 58, places 48 volt battery over the sleeve conductor to energize relay I04 and I in series. Assuming that the operator desires to ring station I, she depresses key I02 placing twenty-four volts on the sleeve conductor instead of fortyeight volts. Whereupon relay I05 will release and close a circuit from ground through contacts I06 and I 01 to ringing relay I08. Relay I08 upon energizing causes thirty-three cycle alternating current to be applied to the line actuating the harmonic ringer 56 at station I. The ringer 51 will not respond to thirty-three cycle current.

However relay I09 in the oifice equipment 2' controlled by the ringing key in the cord circuit will upon energizing cause sixty-six cycle alternating current to be applied to the line for actuating the ringer 51.

The subscriber at station I upon removing the receiver from its hook closes a circuit intermittently as previously described, through relay es. This relay is designed for slow release and will maintain its contacts closed during the interruptions of the circuit by relay 52 to bring in the visual signal H0 in front of the operator. The operator upon answering'the call by plugging into the jack 58 will cause relay I04 to be energized to close its contacts, thereby short eircuiting relay 59 to retire the signal. Likewise a subscriber from station I can signal the operator at 2'.

From the above description it has been shown that two secret conversations may be transmitted over a pair of conductors from subscribers station to the telephone Office at the same time.

The equipment of Figure 3 and Figure 4 may be used in the trunk line between two central oflices shown in Figure 2. In Figure 3 a jack may be connected at contacts 5 and 8 in place of the subscribers telephone and the ringers 56 and 5'! may be replaced with ringing current drop signals in the switchboard.

Equipment at subscribers station I and ofiice terminal equipment 2 are arranged for fortyeight volt transmission; station I and office terminal equipment 2' are arranged for twenty-four volt transmission. In other Words, station I always operates over forty-eight volt line, and station I always operates over twenty-four volt line.

In the various circuits shown and described I have simplified the drawings by indicating the source of potential as a positive sign. I have also indicated certain similar apparatus by primed numerals.

The embodiments of the invention which have been given herein are illustrations of how the various features may be accomplished and of the principles involved. It is to be understood that the invention contained herein is capable of embodiment in many other forms and adaptations, without departing from the spirit of the invention and the scope of the appended claims.

Having thus described my invention, I claim:

1. In a telephone system, a subscribers line, sources of high and low potential direct current, means for connecting said sources of current in successive rotation to said line, a supervisory lamp, means for closing a circuit from said source of high potential current over said line during certain alternate periods of time to cause said lamps to glow,'means for varying the highpo- ,tential current in said line in accordance with a telephone message during other alternateperiods of time, and means for varying the low potential current in said line in accordance with another telephone message.

2. In a telephone system, a trunk line, sources of direct current, means for supplying current from said sources in successive rotation to said line during substantialy equal periods of time, a plurality of supervisory lamps, means for closing a circuit from a first one of said sources of current over said line during certain alternate periods of time to cause one of said lamps .to glow, means for closing a circuit from a second one of said sources of current over said line during certain intermediate periods of time to cause another one of said lamps to glow, means for varying the current in said line from said first one of said sources during other alternate periods of time in accordance with one telephone message, and means for varying the current in said line from said second one of said sources during other intermediate periods of time in accordance with another telephone message.

3. In a telephone system, a trunk line provided with sources of reiatively high and relatively low potential direct current intermittently applied, a pair of supervisory lamps, means for closing a circuit from said source of high potential over said line during certain high potentialperiods of time to cause one of said lamps to glow, means for closing a circuit from said source of low potential over said line during certain low potential periods of time to cause another one of said lamps to glow, devices associated with one end of the trunk line for grouping and combining received signals from different messages to vary the high and low potential current in the said trunk line above the original frequency for' the said signals to transmit one message during other high potential periods and another message during other low potential periods, and other devices associated with the opposite end of the trunk line for separating and expanding the grouped signals for the different messages into substantially their original intervals.

4. In a telephone system, means to separate and group received sound signals in alternate periods of time, means to separate and group other received sound signals inintermediate periods of time, each of the said first and second means comprising a device for recording said signals on a movable member, and a movable device adapted to travel in a direction opposite to said member for reproducing said signals in spaced groups, a generator for producing spaced control signals, and means responsive to the control signals for controlling the movabTe devices to govern the starting time for each group of said signals, a subscri'bers line, a number of difierent sources of direct current intermittently applied to one line terminal, means at the opposite line terminal to close a circuit from a first one ofv said sources of current over said line during said alternate periods of time, means to vary the current in said line in accordance with said soundsignals grouped in said alternate periods, means at said opposite line terminal to close a circuit from a second one of said sources of current over said line during said intermediate periods of time, and;

means to vary the current in said line from said second source in accordancewith saidsoundsignals grouped in said intermediate periods.

5. In a telephone system, a trunk line provided with a source of direct current during alternate periods of time, a supervisory lamp, means for closinga circuitfrom said source of current over said line in certain of said periods to cause said device associated with the opposite end of the trunk line for expanding the grouped signals to substantially their original interval.

6. In a secret telephone system, a party telephone line extending to a central ofiice provided with at least a first subscribers station and a second subscriber's station widely separated, two

sources of direct current at the telephone office intermittently applied tosaid line during recurringperiods of time, a station call indicating lamp at the central office for each of said stations, meansat the first station to close acircuit from one of said sources of current over said line during certain alternate periods in said recurring periods to cause one of said lamps to glow, means at the second station to close a circuit from another one of said sources of current over said line during certain intermediate periods in said recurring periods to cause another one of said lamps to glow, means at each of said stations actuated by current from one of said sources to control the transmitting periods of both of said stations so that only one station transmits at a time, means at the first station and means at the second station to vary the current in said line in other of said recurring periods in accordance with two. telephone. messages without overlapping.

I. -In a telephone system, a party line extending to a telephone office provided with a plurality of subscribers stations, at source of direct current at the telephone ofiice, means to connect said source of current to said line in spaced recurring periods of time, a call signal at each subscribers station, a source of ringing current at the telephone ofiice, means to disconnect said source of direct current and to connect said source of ringing current to said line during certain of said recurring periods to actuate the cal signal at a first one of said stations, means at the said first station to close a circuit from said source of direct current over said trunk line during other of said recurring periods, means at the said first station tovary the direct current in said line during certain periods of time in accordance with a telephonemessage, and means at a second one of said stations under control of current from said source of direct current received over said line to control the transmitting period for said second station.

Vided, with an armature and a pair of contact vsprings, for closing an energizing circuit to said electromagnet, one of said springs actuated to engagev the other said spring by a relatively small movement ofiits armature and releasing means actuated upon fullmovement of itsarmature to disengage said springs for opening said energizing 'circuit', and means at said ofiice to connect ,a source of current intermittently for said line to 9 energizing said relay, thereby controlling the movement of said mechanism for transmitting said signals in predetermined periods of time.

9. A relay comprising a movable armature and an electromagnet to actuate said armature, a pair of contact springs, a ratchet secured to said armature adapted to engage one of said springs, whereby a relativefy small movement of said armature causes said springs to contact, and means to actuate said ratchet upon substantially full movement of said armature to disengage said prings.

CHARLES H. HOMRIGHOUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 789,769 Summers May 16, 1905 840,120 Donning Jan. 1, 1907 913,521 Latour Feb. 23, 1909 1,234,864 Brown July 31, 1917 Number Number 10 Name Date Gherardi Dec. 25, 1917 Wilbur et a1. Jan. 11, 1921 Mathes Feb. 23, 1926 Hartley Apr. 12, 1927 Traver Aug. 14, 1928 Johnson et a1. May 24, 1932 Nemirovsky Jan, 2, 1934 Baird Feb. 6, 1934 Eickhoff Aug. 14, 1934 Riggs July 21, 1936 Loth et a1 May 11, 1937 Smith Jan, 11, 1938 Gabrilovitch Jan. 11, 1938 Henroteau Feb. 27, 1940 Vroom May 28, 1940 Skillman Nov. 18, 1941 Henroteau Mar. 3, 1942 FOREIGN PATENTS Country Date Great Britain Oct. 12, 1923 Germany Jan. 30, 1930 

